An active energy ray-curable ink has been characterized as an ink exhibiting excellent environment friendly printing and excellent printing efficiency as well as providing printed matter of a high quality since the ink is of solvent-free type and is cured and dried instantly by radiation of active energy rays. Accordingly, such an active energy ray-curable ink has been developed for use in a variety of printing methods such as offset printing, screen printing, flexographic printing, and/or inkjet printing (for example, please refer to Patent Document 1).
The active energy ray-curable ink is generally obtained by mixing a dry pigment with a radical polymerizable varnish, a radical polymerizable monomer, a photopolymerization initiator and the like, followed by kneading and dispersion by using a roll mill or the like. However, there has been problems such that the method might cause gelatinization when the radical polymerizable varnish and/or the radical polymerizable monomer are kneaded and dispersed by a roll mill under a strong shearing force, and that it normally takes more than 24 hours for dispersion by a roll mill.
Moreover, even though such a long time has been spent on preparation, pigment dispersibility is poor and printability is occasionally poor when the obtained ink is utilized in offset printing.
As a method for obtaining an active energy ray-curable ink without using roll mills, an active energy ray-curable ink using a dispersed element of pigment obtained by dispersing a pigment in a radical polymerizable varnish using a flushing method has been known (for example, please refer to Patent Reference 2). However, this method requires a special varnish in which a value of n-hexane tolerance is adjusted to be 4 or more.    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2002-309142    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2003-342514